This invention relates to a process for purifying waste gases containing polyhalogenated compounds, by adsorption, wherein the adsorption agent loaded with harmful substances is transported under an inert gas to another processing step or to storage.
In flue gas purification systems associated with heating and power stations and garbage incinerators, adsorption stages employing activated carbon, activated coke or lime-carbon mixtures are used to remove harmful substances such as, e.g., mercury, dioxins and furans. The activated carbon is, for example, derived conventionally from lignite; activated coke is obtained conventionally, for example, from anthracite coal; and lime-carbon mixtures are commercially obtainable. Other adsorption agents having an affinity for the harmful substances can also be used.
After the adsorption agent is loaded with harmful substances as a result of the flue gas purification, the loaded agent must be stored so it can then be disposed of or transported to another site. Generally, the disposal comprises dumping of the waste.
Whereas this type of flue gas purification by adsorption solves the gaseous emission problem, a new waste and safety problem occurs in the form of highly toxic contaminated adsorption agents. Heretofore, the adsorption agent, e.g., activated carbon or activated coke, was stored in silos and then fed in batch amounts pneumatically, mechanically or by silo trucks for thermal utilization within or outside the installation. For thermal utilization, there were commonly employed furnaces, especially slag tap furnace, but other conventional equipment can also be used. In the case of the lime-carbon adsorption agent, because of the high salt content therein, it has to be fed to a physical-chemical pretreatment to render it inert before dumping. It is also known that for safety reasons storage and transport have to take place under inert gas protection in order to prevent spontaneous combustion of the particulate carbon as well as the emission of desorbable toxic pollutants. But the toxic potential remains, giving rise to additional safety and environmental protection problems.